I. Field of the Invention
This invention relates generally to high capacity, industrial and agricultural ventilation fans. More particularly, my invention relates to an improved, motor-mounting system for belt-driven fans that continuously maintains and regulates belt tension.
II. Description of the Prior Art
High volume fans provide ventilation and cooling for many agricultural facilities, especially in the poultry and dairy industries. Such fans are designed to properly control the direction, velocity, and volume of air being moved. I have previously proposed a fan adept at controlling air over long ranges. One of my previous fan inventions, issued as U.S. Pat. No. 5,480,282, on Jan. 2, 1996, and its teachings are hereby incorporated by reference. It was classified in U.S. Class 415, subclass 125. As can be seen from that patent and the prior art therein, the known prior art comprises many different types and designs of fans adapted to satisfy various criteria.
High volume ventilation fans include a rigid housing that protectively encloses the fan blade and motor. Protective guards shroud the housing. So-called "box fans" have a tubular housing that is "square," i.e., in the general form of a cube or parallelepiped. A tubular, cylindrical housing, in the form of a cylinder, is used by so-called "barrel fans," Depending upon the design and configuration, a number of different accessory items such as screen guards, shutters, electrical controls, discharge cones, and venturis may be deployed. Typical high capacity fans may be mounted on the ground, or secured in an elevated position upon an adequate support. The two principal fan-drive designs employed with modern high capacity fans are direct drive and belt-drive systems. Both arrangements have advantages and disadvantages.
Such fans are often deployed in rugged, industrial environments, where they may be used for long hours without periodic maintenance. As dust and dirt accumulate, vibrations develop, causing various parts to loosen. Obviously moving parts such as motors, belts, and rotors will wear with time. Periodic maintenance, while desirable, will be lacking in many industrial or agricultural applications. When maintenance is performed, the servicing technician faces a number of problems. The design features and differences between various fans used in a given application make it difficult to inventory proper parts, tools, and service diagrams. The servicing technician must possess knowledge of several different types and designs of fans. Another problem involves the protective safety guards installed on most fans. These must be removed to expose the fan's innards for service. Over time, the guards can vibrate loose, and in response to vibration and rough handling, they may become deformed and difficult to remove or adjust.
In general, the more a fan is used, the "looser" the guard and fan housing becomes. Often the housing is warped or damaged over time, and as a result, the guards simply do not "fit" as tightly as they did when the fan was newer.
Typically belt-driven ventilation fans have drive assemblies that are mounted on spaced-apart bearing/shaft assemblies. A drive motor is typically mounted such that its axis of rotation is parallel to and spaced apart from the fan shaft. The motor and fan shafts are connected by a suitable "V" belt entrained over pulleys that establish an adequate gear drive ratio. Many structural variations for mounting the fan, the motor, and the linkage components have been proposed. A major problem with belt-driven fans is the lack of a simple belt tensioning method.
As high capacity ventilation fans age, accumulating wear on the belts, motors and associated pulleys can loosen critical parts. When belt wear becomes appreciable, belt tension varies unpredictably, degrading performance. To maintain peak operating efficiency, belts in common designs must be inspected, and the apparatus must be adjusted relatively frequently. Unfortunately, this type of routine maintenance requires considerable time and effort. Tension adjustments to belt-driven fans generally require the removal of at least one guard. Consequently, structure that maintains belt integrity and reduces service requirements is desirable. A reliable system for automatically maintaining belt tension in a belt-driven fan would increase reliability, and optimize efficiency.